Scratch another item off Danny Ainge‘s to-do list. Multiple outlets are reporting, and WEEI.com has confirmed, that the Celtics have signed free agent center Jermaine O’Neal for two years at the full mid-level exception.

O’Neal’s addition shores up the center spot, which is in flux following Kendrick Perkins‘ knee surgery and the expected retirement of Rasheed Wallace. By using the full MLE, the Celtics now are shopping for players with the the veteran minimum contract and the allure of playing on a championship contender.

The length of O’Neal’s deal also completes the framework of the Celtics’ window of opportunity with their veteran group. O’Neal’s deal will expire at the same time as Kevin Garnett‘s and Ray Allen‘s. (Allen has a player option for the second year).

As noted earlier today, Ainge still has Wallace’s contract to dangle in trade talks, should Wallace follow through on his intention to retire. Ainge can also re-sign his own team’s own free agents, with Tony Allen figuring to be the next Celtics target.

Allen’s contract is a coup for Danny Ainge and the Celtics and it’s also an indication that Allen understands the shifting landscape of the NBA. Allen wasn’t in the market for the proverbial last big contract. He needed a place where his skills could flourish, even at age 35.

He also left himself an out if the Celtics struggle, Rivers decides to leave and a new collective bargaining agreement works in his favor. The Celtics meanwhile have left open a two-year window until Kevin Garnett‘s contract expires. It really is a win-win deal for both sides.

The NBA has set the cap for next year at a tick over $58 million, about $2 million more than was expected, and lifted the moratorium on transactions. Many of the big name players have already decided (with a certain big one still to go Thursday night) and the big work for Ainge and the Celtics is done.

The starting five is under contract along with Glen Davis, first-round pick Avery Bradley, Turkish center Semih Erden and Rasheed Wallace. More on Sheed in a minute, but it’s worth pointing out that Philly legend Sonny Hill told the Globe that Wallace might be re-thinking his decision to retire.

Beyond that, Oliver Lafayette and Tony Gaffney have non-guaranteed minimum-level deals, and there’s also second-round pick Luke Harangody, who has not signed a rookie deal yet. Keeping Wallace where he is for a moment, that’s 12 players if all of the rookies make the final roster.

Now Ainge has to get creative.

Keep a few things in mind. The Celtics are over the cap and they used the bi-annual exception on Marquis Daniels last summer. That leaves the mid-level exception, valued at $5.765 million, and veteran minimum contracts.

The Celtics made O’Neal look terrible in the playoffs, but he’s younger than Miller and Shaq and, playoffs aide, O’Neal had a good season with Miami in 2009-10. He appeared in 70 games for the first time since 2003-04 and he shot over 50 percent for the first time in his career en route to averaging 13 points and seven rebounds a game.

It’s expected that the free agent logjam will open up once LeBron James make his decision Thursday. O’Neal was not expected to re-sign with the Heat, an expectation that became reality once Chris Bosh announced he was going to Miami with Dwyane Wade.

Now that Doc Rivers and Paul Pierce are back in the fold, the next logical move for Danny Ainge is to work out a contract with Ray Allen. The Celtics want him back. They can offer him the best deal, and Allen has said that he wants to return. But it’s not always that simple.

James is said to be unsure of whether he will return to the Cavaliers or take an offer from one of the other teams that is pursuing him — the Knicks, Nets, Bulls and Heat. (It’s safe to assume the Clippers took themselves out of the running, if they were ever a serious option to begin with).

If James does stay in Cleveland, the Cavs would only have the mid-level exception to offer Allen and they also need help in the center department. If James goes elsewhere, those teams would have cap money to spend on supporting players, but they are all basically building teams from scratch and it’s unclear how much of that precious cap room they would be willing to use on Allen.

Both the Knicks and Heat are in desperate need of point guards, while the Nets would have to bring along an expensive power forwards to entice James. The Bulls may be the wild card in this scenario since they have a ready-made team in place for either James or Dwyane Wade, and Allen already has an existing relationship with new coach Tom Thibodeau.

In the end, there may not be a huge deal waiting for Allen when the dust settles, but shooting is always at a premium, and Allen and Mike Miller are the two best shooters available in free agency.

So, the Celtics will wait it out. Because they have Allen’s “Bird rights,” they can go over the cap to re-sign him and don’t have to use the MLE. The key for Ainge isn’t the dollars, however, it’s the years.

Allen will turn 35 this July, and the track record for shooting guards that old is not great. The Celtics are gambling that Allen’s commitment to conditioning will carry him through the latter part of his career and he will be more Reggie Miller than Mitch Richmond, which seems like a decent probability.

A two-year deal would be ideal, but with competition for his services, they may have to go to three. Ainge showed his resolve to bringing the Celtics core back together when he went four years on Pierce’s new contract. If he did go to three for Allen it would allow him to go year-to-year with the veterans as Kevin Garnett‘s contract is up after two more years.

The Celtics won’t be able to be under the cap anytime soon when all this is over, but they may be able to reduce their luxury tax bill, which would also make it easier to continue adding veteran pieces this summer or at the trade deadline. There will also be a new collective bargaining agreement in place after next season, which could significantly alter the NBA landscape.

There is much uncertainty around the NBA these days, but the Celtics’ path is clear. It just may take a few weeks for it to come into sharper focus.

The Celtics announced their roster for the Orlando Summer League and there is a very intriguing name on it: Turkish center Semih Erden.

Danny Ainge suggested before the draft that the time may be right for Erden to play in the NBA. The Celtics have held his rights since selecting him late in the second round of the 2008 draft. Erden could have a role on the 2010-11 Celtics, who are starved for height.

Erden will be joined by Tony Gaffney and Oliver Lafayette, who joined the team late in the season. Their contracts are not guaranteed for next season and a strong showing in the summer league is a first step toward earning a roster spot.

Second round pick Luke Harangody will also play, but first round pick Avery Bradley will not. He will have a scope performed on his left ankle and is scheduled to be out six to eight weeks.

Multiple outlets are reporting that the Celtics have reached an agreement with Paul Pierceon a new contract that will likely keep him in Boston for the duration of his career. A source told Jeff Goodman of WEEI.com/FoxSports.com that the total package would be worth $61 million over four years, with all four years guaranteed.

Pierce left $21.5 million on the table for next season by terminating the final year of his contract and the new deal gives him certainty in what promises to be an uncertain NBA. The collective bargaining agreement is set to expire after the 2010-11 season, and the expectation is that the owners will try to rein in player’s salaries.

Pierce’s new deal will take the Celtics over the salary cap, but it may provide some luxury-tax relief in the long run, which is no small consideration.

There are risks for the Celtics. Pierce will be 36 years old in the final year of the deal, which can’t be finalized or officially announced until next week. It will also take him well beyond Kevin Garnett’s contract, which has two seasons remaining.

But four years is the cost of keeping the team together for another run at a championship and that has been Danny Ainge’s plan all along. Doc Rivers elected to return for the final season of his coaching contract earlier in the week, but the work is only half done. Read the rest of this entry »

WEEI’s Michael Holley has confirmed through a team source that Doc Rivers will return to coach the Boston Celtics next season.

The Herald’s Steve Bulpett was first to report the story.

This is very encouraging news for the Celtics and Danny Ainge as he attempts to bring back the core of the team for another run. The veteran players had all expressed support for Rivers while he took some time to consider his options.

While Paul Pierce has decided to terminate the final year on his contract and joins Ray Allen as a free agent, Rivers return is a significant factor in their decision-making.

It also allows the Celtics a degree of stability in what has been an eventful few weeks since their loss in Game 7 of the NBA finals against the Lakers.

In addition to Pierce’s decision, Tom Thibodeau was introduced as the head coach of the Bulls ending what had been a very successful three-year relationship between Rivers and his assistant. Also, Kendrick Perkins told reporters Tuesday that he would have surgery to repair a torn Anterior Cruciate Ligament in his right knee and would probably be out until late December or January.

What isn’t known yet is whether Rivers would consider extending his contract beyond next season. But with the start of free agency Thursday, his return eliminates some of the guesswork for potential free agent targets and also increases the likelihood that veteran players who miss out on big contracts would sign with the Celtics.